Signaling system



Sept. 22, 1936 EQJ. lvlccAm-HYy l l 2,054,827

-" v SIGNALING SYSTEM l Filed July 2, 1952 l l l 'f7 y yf Patented Sept. 22, 1936Y Pars-NT orties Y 2,054,827' v yslomeIlmo. SYSTEM dxrard; J ,ll/ibirilia vluewtni.,zllavsss asignor, ,to The Gamewell ompany,A NewtonUpper Falls, Masssa corporation of Massachusetts yApplifatimi July 2, 1932, serialim. 620,666 7 claims. `(o1.'177``367') Certain signaling systems, as forexarnplare alarm and-similar installations, operate by interrupting normally closed' 'and energized signaling' circuits Withappar'atus'in series connection. Such systems havetoy be arranged ffor'service under faulty 'conditions of various kinds,I like grounded, interrupted.' or fshunted lines, and in: some instances they are for that purpose equipped f for signa-ling' through Van emergency conductor,

- usually thefground; which can be associated, if thev necessityf-arisesywith any of the signal transmitting stations; either by hand or automatically. In systems of this type, the signal* transmitters,

referred to as alarm boxes, connect the signal l5 circuit to ground, sometimes only during signaling with' systems ofthis type, which are adapted" to take care of almost any possible. emergency condition, itis nevertheless possible that yin spiteY of the use 'of alarm boxes incorporating/the well known non-interference and succession features, a'transmittingor receiving stationi'may bevirtually eliminated 'from the signaling" circuit. For example, iif'two points Vof a' r' alarm circuit are simultaneously" grounded, these ground connections may establish a shunt around intermediate boxesl or stations asire houses with acoustic signal receivers, th'erebyrendering the shunted apparatus inoperative, as willgbe explained `in detail hereinafter. It' is,l therefore, onev ofVV the principal objects ofthe present invention toV provide' a signaling syst-ern, and sig'na'ltransmitting equipment-therefor, Which eliminate, the danger of shunting out' signaling apparatus intermediate In another aspect; the present invention permits the use of comparatively 'simplesignal initiating' 'apparatus' which nevertheless, in circuits of thl'kind referred-to, V'provide 'a degree 0f certainty and security-.of une' operation'- ofV their ,V noneintrference and: 'succession' equipment. This advantage is obtained-byorganizing the signaling circuit s'uch a manne 'at'the *giuiiling"of` a Signartransmitter duf A ormai operationcan' not iniluenc'e theop'eration of 'theseI a-'fonemen'-- tioned devices. Accordingly, other otjectsoflthe present invention are to providefa ysign'al'ir'igcir- Cllil; 0fT the type referredtbjwlosfwelfion ifsj not detrimentally inuen'ced 7' a'r signal' transmitter during Whereas it permits emergency 'opera'tionfvv or' alVV operag-round as Yeniergeiicy"con'duotoi,-to proifidealarmf "1";

boxes vvhich prevent anyflowof a certain kind of current, for example directeur-rent, to vanenergency'cdductor; whereas theypermit the corresponding flow of' another kind ofV current, for' example alternating current,` and to 'provide ra signaling circuit Whichtpermi'ts the improv ofv existing alarm systensm'erely by adding-s mi` ple'and inexpensiveiel'ements to the oldinstallai tion.4 Y 'I'fhese l and f vother objects and" advantages4 are' obtained byeonnecting-in the ground' pathofvv signal initiating devices or' alarm boxes sedln circuits employing differentftypesfof" current for normal and" emergency signaling; devicesy which prevent. the flow throughzth'e emergency; con?v d'uctor ofthe current which isonly intendiedffoi"` normal operation, 'as-Will 'be explainectinv detailiin'.' the following description of'twol-embod-imentsof the invention by Wayof example, Withfrefere'nce' to the appended-drawing; in which: 31611 Fig. `1 is a connection vdiagramof a rire alarm installation with separate alternating vcurrent 'andi directfcurrent supplies, incorporatingth-e present invention; and

Figa 2 is a similar diagram :showing the inventionappliecl'toia diierent current supply system, and under different emergency conditions.

Fig, 1 showsfa circuit Aemployingdirectcurrent and .alternating current for j normal and emergencyV operation, l respectively, according to; the above-identiiied copendng applicationpf Frank- R. Bridges, Serial No; 620,683. This ci-rcuit comprisesa circuit loop with stationlterL min'als I and 2, signal transmitting and signal' manifesting, devices'represen'ted ingFigl by 4g alarm boxes M, N and O- and-bell the latter symbolizing the acoustic signalfmanifestfngde,-A vice of are house which-,maybe included in signalloopL'. Asrdescrib'ed in detailing-the above-x identiedcopending application;y loop L is supi plied with alternating currentn from` a" transformer T whose vsecondary 4;, is`V connected-.tocground' and overrlea'ds-:S andi Sito terminalsvv` IV and 2, Whereas theprimaryaSis supplied from..

a suitable alternating current-source'. Condens` 5g 3' ers 'I and 8, and choke coil 9, respectively, prevent interference of the two current supplies. Signal manifesting devices II, I2 and I3, as for example, directly recording instruments, or relays of repeater circuits, are connected as indicated in Fig. l, and herein referred to as recorders.

The alarm box M, shown in detail in Fig. 1, is representative of the type of signal transmitters which ground the signal circuit during each signaling period, but it is understood that my invention may be applied to other types of alarm boxes.

Box M is somewhat similar to the signal transmitter disclosed in Patent No. 1,244,587 for Successive non-interference box to F. W. Cole, dated October 30, 1917, but has additional means for sending signals through ground as the emergency conducto-r. It comprises shunting contacts 8|, normally closed signaling contacts 84, 85, and normally open contacts 82 and 83, both pairs of contacts being operated by the code wheel 88. As indicated in the drawing, an insulating block 81 is arranged intermediate levers 82 and 84, so that lever 82 can move independently of 84, if the latter is retained in raised position by pin associated with the armature of non-interference magnet (operative only with direct current) in such a manner that 83 moves underneath 84 Yif the armature is deenergized. Normally codeV signals-are sent by contacts 84 and 86 opening and closing in accordance with the code represented by the teeth of wheel 88 whereas, if the lineV is interrupted due either to Va line break', or the fact that another box is already signaling, magnet 85 is deenergized and its armature drops; moving'pin 8|! underneath lever 84,`

be interposed between contacts 82, 83 and ground,

as for example, indicated by condenser 90 shown in the other boxes. The disposal of the condenser or condensers willmainly be governed by the design'of the alarm box withV which they are used. In the present case the condenser arrangement oifers alterating current paths tof ground from both sides of the line, these paths including only the groundingswitch and not the non-interference coil. If only a single grounding condenser is used, it must be connected between one of the two terminals of the alarm box in series with switch 82--83, in order to avoid a continuous short circuit which would exist if the single condenser were connected between groundV and contact 83 of Fig. 1, by omitting condensers 9| and 92. Itwill be evident that under certain conditions, as for example when signaling.

shown for alarm -box M of Fig. 1, theemergency `circuit includes only contacts 82-83 and the recurrent from any suitable source.

spective condenser, no matter how the emergency circuit is constituted, so that emergency signaling is rendered more certain.

In the modication according to Fig. 2, L is again an outer signal circuit or loop, including alarm boxes M, N and O and manifesting station F, and leading to station terminals I and 2. A rectifier bridge R has four terminals 5|, 52, 53 and 54 and four asymmetric conductors 6|, 62, 63, and 64 which permit the passage of current substantially only in the direction of the arrows or their symbols. Terminals 5I and 52 are connected to the secondary 59 of a transformer S whose primary 58 is supplied with alternating Terminal 52 is groundedY through signal manifesting device 43, and manifesting devices 4'I and 48 are connected in the leads from terminals 53 and 54 to terminals I and 2. In a system of this type, the loop L is normally supplied with direct current derived from terminals 53 and 54, whereas under certain emergency conditions, when the loop L is grounded either through themechanism of an alarm box or due to a faulty' line, alternating current impulses Vflow between terminals 52 and/or 53 and 54, respectively, as described and claimed in the above-identified copending application Serial No. 573,151.

Referring to Fig. 1 the operation of my signaling system under normal conditions Vis as follows: If a single box, for example M, is pulled, switch 8| opens and signaling takes place with direct current, contacts 84 and 86 interrupting the normally closed circuit, thereby initiating signal manifestations at centrally located receivers, as for example, recorder or relay I3, and also at alarm devices included in the signal loop, as for example, bell F. The grounding of the circuit through contacts 83 and 82, condensers 9|, 92,V

is inconsequential as far as reception at I3 is concerned, since the direct current is arrested at 9| and 92, and the direct current circuit therefore is not disturbed by the closing of contacts 82-and 83. Recorders II and I2 will receive the same signals, given at contacts 82 and 83, andv transmitted through condensers 9|, 92, ground an-drsecondary 4.

If several boxes are pulled at almost the same time, the rst box takes'possession of the line,

whereas the non-interference mechanisms ofV all boxes which may be pulled later preventthese from interrupting the normal signaling circuit by retaining lever 84. in raised position. Again, the grounding at 82 and 83 is inconsequential due to the fact that direct current can not flow to ground over the condensers. Recorders II and I2 will receive alternating current signals as above described. V

Assuming that boxes without condensers are used, one of the advantages of my invention will be apparent fromY the` following consideration. If, for example, box N is pulled rst, and boxes M and O subsequently, the'non-interference devices of N and O arrest contacts 84 and 86 of their respective boxes, but the grounding contacts 82 and 83 of M and-O shunt box N for. direct current and interrupt its signaling, the signals at the central station as well as at F becoming unintelligibly garbled. With condenser equipped boxes according to the present invention, direct current circuits includingl the ground can not be established, whereas the alternatingl current can not interfere with proper signaling (although it is Vshort circuited over the condansent-.since the nga-interference:neerlegt-are rllyfr. esitate agencement-,5 Y In case tf. en @cemetary er@ -need-.dreun asiindicetedfat e 0f Fia 1,. conditions are/similtl'i and ,iflllfllrfefen @Qllpmem .as Well S linefmanifestigg. .devices Operate propenyY with. directcurrent whichpan not flow over ground, there lbeing only one ground .connectionavailable fcnthe directlcurrent, namely x. l .Assuming `that y boxes without condensers are usedacondition similar to thatabove Idiscussed would arise. vWith*anaccidental groundat V2:, ,bQX N Operating, andzbox M subsequently pulled, M andground r' wouldshunt .N, box'Mlinterrupting .the signalingfo N, which is 'especially undesirable if it occurs during any portion of the code signal transmitted by N.

vIf ithe circuit vShould be accidentally broken, as, indicate-,d at Vyof Fig. yl, the direct current is interrupted yand the system would bjelinoperative without the presence-of an alternating'current circuit. s In l this case, assuming that vfor example box M is pulled, Yalternating current is transmitted by contacts l82 and 83 through the condensers and ground, and received by recorder i i. The non-interference apparatus'does not respond to. alternating currentand does not, therefore, operate under these emergency conditions.

Bells intermediate the power supply and the operating box function normally, provided they respond to alternating current.

In case of a short circuit e, as indicated in Fig. 2, the shunted apparatus N and F carry no direct current, which is diverted through 2, so that no direct current signals originating with N can be received. However, contacts 82 and V83 transmit alternating current signals through ground, as above described, the signals being received at 46 and at F. Under such conditions the non-interference features of the shunted boxes are inoperative, whereas the boxes outside of the short circuit function normally with direct current, and therefore also with non-interference.

A further advantage of my new systems consists in the favorable influence of the box condensers with respect to stray currents. It is a well known fact that the circuits of grounded re alarm systems are often disturbed by stray currents originating, for example, in trolley lines. Such unidirectional stray currents are successfully excluded from the normal operating circuits by condensers arranged according to the present invention as will be apparent from the preceding description without further explanation.

Also, the new arrangement affords a protection against the harmful effects of accidental contacts with high power alternating current lines. Assuming that the boxes are not provided with condensers, and that an alternating current line H accidentally touches the signaling loop as indicated at wi of Fig. 2, the alternating current of H would pass to ground through the station and damage the apparatus of the latter. The box condensers according to my invention, however, offer alternating current paths to ground so that the alternating current of H is diverted from the station due to the fact that the station impedance is high compared to the box impedances. The normally open grounding contacts 82 and 83 are thereby easily bridged by the power current, especially if the gap between these contacts is accordingly dimensioned.

It will be apparent from the foregoing description that the underlying principle of my intentions-namely, theseperetion .ofacermegend emergency epereton, 0f-Signal mit. tins,... t by making their ground @QliieiiQn-:Qlleatlieirfenlv fertile emergency Current, may be. Carried-cut in -wayS .dilernt .from these .herein disclosed.' For example, V,differentv alarm AAbox mechanisms maybe used, or asymmetric conducto.r sas for example rectifiers, vmay be employedfinstead of condensers for .excludingndirectcurre'nt from` groundfor two alternating currents fof different' frequencies kmay be used, whereby one` frequency can be .excluded from ground vby suitable filtering equipment. i

It should be understood that thepresent diselosure is `for thelpurp'ose of Villustration only and "that .this invention includes Aall modifications and equivalents which fall within the scope of the appended claims. ,Iiclaimz' 1. Aiire'alarm box for signalingsystems operating lwith direct and alternating currents comprising two line terminalsa normally closed line signaling switch and a non-interferencegmagnet operating only on direct current in seriesacross saidterminals, meansl controlled by said magnet upon"deenergization thereof .for arresting said line signaling switchin closed position', two condensers serially connected across said terminals, a ground signaling switch intermediate ground and a point of the conductor connecting said condensers, and signal initiating means for opening and closing respectively said switches in synchronism, said condensers forming withsaid ground signaling switch paths exclusive of said 36 line switch and said magnet.

2. A re alarm box for signaling systems operating with direct and alternating currents comprising two line terminals, a normally closed line signaling switch and an exclusively direct current operative non-interference magnet connected in series across said terminals, a normally open emergency signaling switch and in series thereto a capacitance connected intermediate one of said terminals and ground, means forconcomitantly but independently actuating said line switch and said emergency switch, and means controlled by Vsaid non-interference magnet for arresting said line switch in closed position upon deenergization of the magnet.

3. A signaling system comprising a normally closedV signal circuit supplied with unidirectional current, an alternating electromotive force between said circuit and ground, individually grounded signaling means serially connected in said circuit for sending signal impulses through said circuit and through said circuit and ground and having means responsive to direct current only for suppressing upon deenergization thereof, the sending of said impulses through said circuit, but permitting the sending of said impulses` ground, and a capacitance intermediate each transmitter and its ground connection.

5. A signaling system comprising a normally closed signal circuit supplied with unidirectional current, an alternating electromotive force between said circuit and ground, signal transmitters serially connected in said circuit including a ground connection, means for despatching signal impulses by opening said circuit and by connecting said circuit and said ground, and noninterference equipment operative only with direct current rendering said transmitters ineffective for opening said circuit but permitting signal despatch through ground, and means in each transmitter for arresting the flow of direct current from said circuit through said transmitters to ground.

6. A fire alarm boX for signaling systems operating with direct and alternating current comprising two line terminals, a normally closed line signaling switch and an exclusively direct current responsive non-interference magnet connected across said terminals, a normally open ground signaling switch connected on one side through a capacitance to each of said terminals and on the other side to ground, means for concomitantly but independently actuating said switches, and means controlled by said magnet for retaining said line signaling switch in closed posi'- tion upon deenergization of the magnet.

7. A signalingsystem comprising a normally closed metallic signal loop serially including two station terminals, direct current responsive signal receptive means, a direct current source, and signal transmitting stations; each station having two line terminals and therebetween in series normally closed loop contacts, and non-interference equipment responsive only to direct current and retaining said loop contacts closed upon deenergization thereof, normally open ground contacts between said line terminals and ground, and means for actuating said contacts to form signal impulses; an emergency circuit serially including the ground', an emergency signal receiver, an alternating current source, one of said station terminals, part of said loop, one of the line terminals and the ground contacts of a signal transmitting station; and in each signal transmitting station condensers intermediate said ground contacts and each of said line terminals for preventing the flow of direct current in said emergency circuit and eX- cluding said non-interference equipment from any possible emergency circuit.

EDWARD J. MCCARTHY. 

